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Why is XOR the default way to combine hashes?
... uniform probability distributions.
This can be seen by writing out truth tables:
a | b | a AND b
---+---+--------
0 | 0 | 0
0 | 1 | 0
1 | 0 | 0
1 | 1 | 1
a | b | a OR b
---+---+--------
0 | 0 | 0
0 | 1 | 1
1 | 0 | 1
1 | 1 | 1
a | b | a XOR b
---+---+--------
...
Where are my postgres *.conf files?
... # analyze
#autovacuum_vacuum_scale_factor = 0.2 # fraction of table size before vacuum
#autovacuum_analyze_scale_factor = 0.1 # fraction of table size before analyze
#autovacuum_freeze_max_age = 200000000 # maximum XID age before forced vacuum
# (change requires re...
Is the SQL WHERE clause short-circuit evaluated?
...on algorithm that takes into account a lot of things (indexes, statistics, table size, resources, etc) to come up with an effective execution plan. After this evaluation, you can't say for sure that your short circuit logic is guaranteed.
I ran into the same question myself sometime ago and my res...
How do the likely/unlikely macros in the Linux kernel work and what is their benefit?
...hese macros only helps the first time code is executed or when the history table is overwritten by a different branch with the same index into the branching table. In a tight loop, and assuming a branch goes one way most of the time, the branch predictor will likely begin guessing the correct branc...
Concrete Javascript Regex for Accented Characters (Diacritics)
...öø-ÿ] // as above but not including [ ] ^ \ × ÷
See https://unicode-table.com/en/ for characters listed in numeric order.
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How to resize a tableHeaderView of a UITableView?
I'm having trouble resizing a tableHeaderView. It simple doesn't work.
19 Answers
19
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When to use SELECT … FOR UPDATE?
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The only portable way to achieve consistency between rooms and tags and making sure rooms are never returned after they had been deleted is locking them with SELECT FOR UPDATE.
However in some systems locking is a side effect of concurr...
Drop data frame columns by name
...multiple variables:
within(df, rm(x, y))
Or if you're dealing with data.tables (per How do you delete a column by name in data.table?):
dt[, x := NULL] # Deletes column x by reference instantly.
dt[, !"x"] # Selects all but x into a new data.table.
or for multiple variables
dt[, c("x","y...
Download file of any type in Asp.Net MVC using FileResult?
... @MohammedNoureldin it is not "figuring" it, there is a simple mapping table based on file extensions or something like that. The server does it for all static files, it is not slow.
– Al Kepp
Jul 26 '19 at 9:59
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ADO.NET DataRow - check for column existence
...
You can simply check like this:
return row.Table.Columns.Contains(columnName);
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